How Do I Smoothly, Gracefully Upgrade from PHP5.1.6 to PHP5.2 on CentOS 5?

At webkeepers.com, they give me PHP5.1.6 instead of PHP5.2. Does anyone know a graceful, smooth way to upgrade from PHP5.1.6 to PHP5.2 and still have things like PDO, MySQL, SQLite, Mcrypt, Mhash, the XML stuff, zlib, curl, and gd to all still work without having to do a bunch of oddball steps?

Also, I see with /cat/etc/issue that I'm running a version of CentOS5 but can't tell if it's 5.0 or 5.1. How do I find that out?

P.S. If you say custom compile, you may find me cower under a rock for several weeks.